St Louis Lambert International Airport (STL), about 25 kilometres northwest of downtown, is the main gateway — served mostly by Southwest Airlines, with direct flights from over 60 US cities and a handful of international destinations. The MetroLink red line runs from the airport into downtown in about 35 minutes for around three dollars; a taxi is 30 to 40.
The city sits at the crossing of two major interstates — I-70 east-west and I-55 north-south — so it is straightforward to reach by car from anywhere in the central United States. Amtrak's Texas Eagle and Missouri River Runner stop at the Gateway Transportation Center near Union Station; the train from Chicago takes about five and a half hours.